Used tires include materials that, if successfully recycled, may be used for a wide variety of industrial uses. However, due to the difficulty in recycling these materials, millions of tires every year are worn out and accumulated. Such used tires if burned cause air pollution. Burying tires leads to landfill contamination. Further, since waste tires are bulky, they take up a significant amount of space, even if compacted. Stockpiling of tires and special treatment of tires in landfills further requires a much more costly operation than disposal of other types of solid waste, such that landfill operators tend to exact a higher charge for disposal of such materials. Such high costs lead to indiscriminate dumping which causes many environmental hazards, from mosquito breeding grounds in the pooling of water within tires to fire hazards since burning tires are very difficult to extinguish as well as a significant eyesore on the landscape.
Tire recapping has declined due to the tendency of more people to prefer steel belted radials. Such tires are more difficult to recap so that most of these tires end up in landfills. Such tires are also more difficult to further process for recycling. Retreading of tires is also not commonly performed on waste tires since the processes are not universally useful on all tires, are still costly and are difficult for steel belted radials. While there have been other uses for used tires, such as for artificial underwater reefs, crash barriers, road building, playground surfaces and the like, these uses still do not satisfactorily use the large number of waste tires generated each year.
Tire pyrolysis processes are known in which tires are destructively heated in the absence of oxygen to produce useful end products such as oils, gases and carbon black. However, there is difficulty in achieving commercial viability for such processes since the costs of recovering the end products is more costly than the costs associated with deriving these materials directly from petroleum. Further, the quality of the carbon black achieved is typically not commercially acceptable. Further, processing problems arise in that pyrolysis results in the generation of fumes that are flammable in the presence of oxygen. Also, under certain conditions, undesired gaseous byproducts may be formed. It has also been difficult to make beneficial use of the end products of pyrolysis for several reasons, including low yields (which render some prior art processes not economically feasible), and poor quality end products (which limits the market for re-sale of such end products). This is particularly true for carbon black end products from pyrolysis which tend to have high levels of volatiles.
Accordingly, there is a need in the art for a tire pyrolysis process which produces marketable carbon and fuel products, and which is economical and commercially viable.
The invention includes a process for pyrolyzing tire shreds, which comprises: (a) feeding tire shreds to a pyrolysis reactor; (b) pyrolyzing the tire shreds in a pyrolysis reactor to produce a gas stream comprising hydrocarbon and a solid comprising carbon; (c) removing the solid comprising carbon from the pyrolysis reactor; (d) directing the gas stream comprising hydrocarbon into a separator; (e) contacting the gas stream comprising hydrocarbon with an oil spray in the separator thereby washing particulate from the gas stream and condensing a portion of the gas stream to oil; (f) removing and cooling the oil from the separator; (g) directing non-condensed gas from the gas stream comprising hydrocarbon away from the separator; and (h) directing a portion of the cooled oil removed from the separator to an inlet of the separator for use as the oil spray in the separator.
Also included within the invention is a process for pyrolyzing tire shreds, comprising: (a) feeding tire shreds to a pyrolysis reactor; (b) pyrolyzing the tire shreds in a pyrolysis reactor to produce a gas stream comprising hydrocarbon and a solid comprising carbon; (c) removing the solid comprising carbon from the pyrolysis reactor; (d) directing the gas stream comprising hydrocarbon from the pyrolysis reactor to a separator for condensing a portion of the gas stream comprising hydrocarbon; (e) directing the solid comprising carbon removed from the pyrolysis reactor into an auger having a pressure in the auger which is greater than a pressure in the pyrolysis reactor; (f) directing a portion of non-condensed gas from the gas stream after step (d) to at least one burner in heat exchange relation with the pyrolysis reactor; (g) burning the non-condensed gas from the gas stream in the at least one burner to heat the pyrolysis reactor and thereby generating an effluent flue gas; (h) extracting a portion of the effluent flue gas; (i) cooling the extracted portion of the effluent flue gas; and (j) injecting the cooled portion of the effluent flue gas into the auger.
A tire pyrolysis system is also included in the invention. The system comprises (a) a pyrolysis reactor having a tire shreds inlet, a solids removal outlet and a gas stream removal outlet; (b) at least one heating element in heat exchange relation with the pyrolysis reactor; (c) a separator having a gas stream inlet in communication with the gas stream removal outlet of the pyrolysis reactor, a liquid outlet, at least one oil sprayer having a sprayer inlet in an upper portion of the separator and a non-condensed gas outlet; and (d) an auger having an inlet and an outlet, the inlet of the auger being in communication with the solids removal outlet of the pyrolysis reactor.
The invention further includes a tire pyrolysis system comprising: (a) a pyrolysis reactor having a tire shreds inlet, a solids removal outlet and a gas stream removal outlet; (b) at least one burner in heat exchange relation with the pyrolysis reactor and having a gas inlet and an effluent gas outlet; (c) a separator having a gas stream inlet in communication with the gas stream removal outlet of the pyrolysis reactor, a liquid outlet, and a non-condensed gas outlet in communication with the gas inlet of the as least one burner; and (d) an auger having an inlet and an outlet, the inlet of the auger being in communication with the solids removal outlet of the pyrolysis reactor system, wherein the effluent gas outlet of the at least one burner is in fluid communication with an inlet of a heat exchanger for cooling effluent gas from the at least one burner and the heat exchanger has an outlet in fluid communication with the auger such that cooled effluent gas can be injected into the auger.